A METHOD OF PRODUCING A MINERAL FIBER WEB, A HEAT CURABLE BONDING AGENT, A MINERAL FIBER CONTAINING PRODUCT AND THE USE OF A HEAT EXPANDABLE AGENT

Abstract: A method of producing a mineral fiber web comprises producing a non-woven mineral fiber web including mineral fibers and droplets or particles of a heat curable bonding agent including a heat expandable agent capable of generating a volumetric expansion of the droplets or particles of approximately 2-1,000 times, preferably 5-500 times, further preferably 10-100 times, by exposure to an elevated temperature, and heating the non-woven mineral fiber web to an elevated temperature so as to cause the droplets or particles of the heat curable bonding agent to volumetric expand for substantially increasing the bonding agent contact between the mineral fibers of the non-woven fiber web and further so as to cause the heat curable bonding agent to cure for bonding the mineral fibers to one another. The heat expandable agent may be a blowing agent or may be constituted by microspheres each comprising a shell of a thermoplastic material within which a fluid agent is confined. The heat expandable agent preferably constitutes approximately 0.02-50 % by weight of the heat curable bonding agent, such as 0.05-5 %, preferably 0.05-1 %, and the heat curable bonding agent including the heat expandable agent constitutes less than 5 % by weight of the mineral fiber web, such as 1-5 %, preferably less than 2 % such as 0.1-2 %.

Description: A METHOD OF PRODUCING A MINERAL FIBER WEB, A HEAT CURABLE BONDING AGENT, A MINERAL FIBER CONTAINING PRODUCT AND THE USE OF A HEAT EXPANDABLE AGENT. The present invention generally relates to the technical field of producing mineral fiber plates. Mineral fibers generally comprise fibers, also known as Man Made Vitreous Fibers (MMVF), such as rock-wool fibers, slag wool fibers, glass fibers, etc. Mineral fibers are usually used for producing mineral fiber products which are used mainly for thermal insulation, fire insulation, fire protection, noise reduction, noise regulation, growth media, etc. More precisely, the present inven¬ tion relates to a novel technique of producing a non-woven mineral fiber web from which mineral fiber-containing plates or products are cut or produced, respectively. The mineral fiber plates produced from the mineral fiber web produced in accordance with the present invention ex¬ hibit advantageous characteristics as to mechanical performance, such as modulus of elasticity and strength, low weight, reduced content of bond¬ ing agents and good thermal-insulating property. Non-woven mineral fiber webs are normally produced as webs, i.e. webs in which the mineral fibers of whπch the mineral fiber web is com¬ posed, are normally linked together by means of droplets or particles of a heat curable bonding agent which is cured by exposure to heat. For providing a mineral fiber web of adequate mechanical performance and mechanical integrity, such as electricity and strength, a certain amount of cured bonding agent has to be present. Hitherto, an excessive amount of bonding agent has normally been used for providing adequate mechani¬ cal performance and integrity such as an amount of bonding agent of the order of 10% - 30% by weight of the bonding agent of the mineral fiber web. An object of the present invention is to provide a novel method of producing a mineral fiber web from which mineral fiber containing pro¬ ducts may be produced which method renders it possible in an online pro¬ duction plant to produce mineral fiber containing plates or products which are of a structure equal in terms of mechanical performance to prior art mineral fiber plates or products still including a reduced amount of bonding agent. A further object of the present invention is to provide a novel method of producing a mineral fiber web from which mineral fiber con- taining products may be produced which method renders it possible in an online production plant to produce mineral fiber containing plates or products which exhibit improved mechanical performance such as modulus of elasticity and strength as compared to similar mineral fiber contain- ing plates or products of the same content of bonding agent. A particular advantage of the present invention relates to the novel mineral fiber containing product according to the present inven¬ tion and produced in accordance with the method according to the present invention which as compared to prior art mineral fiber containing pro- ducts includes less bonding agent and is consequently less costly than the prior art mineral fiber containing products, still exhibiting advan¬ tages as compared to the prior art mineral fiber containing products re¬ lating to mechanical performance and thermal- insulating properties. A further advantage of the present invention relates to the fact that the amount of bonding agent used for producing a mineral fiber con¬ taining product of a specific type is reduced in accordance with the method according to the present invention as the amount of bonding agent may be reduced in a mineral fiber containing product according to the present invention as compared to a prior art mineral fiber containing product of similar properties in terms of mechanical strength and thermal-insulating properties. A particular feature of the present invention relates to a unique application of the heat expandable agent constituting a component of the heat curable bonding agent to be used in producing mineral fiber pro- ducts according to the present invention in accordance with the method according to the present invention providing a reduction of the amount of heat curable bonding agent needed for providing a mineral fiber con¬ taining product of a specific mechanical performance further exhibiting a reduced inflammability as compared to a prior art mineral fiber con- taining product of identical or similar mechanical performance. The above objects, the above advantages and the above feature to¬ gether with numerous other objects, advantages, and features which will be evident from the below detailed description of preferred embodiments of the invention are in accordance with a first aspect of the present invention obtained by a method of producing a mineral fiber, comprising: producing a non-woven mineral fiber web including mineral fibers and droplets or particles of a heat curable bonding agent including a heat expandable agent capable of generating a volumetric expansion of said droplets or particles of approx. 2 - 1,000 times, preferably 5 - 500 times, further preferably 10 - 100 times, by exposure to an elevated temperature, and heating said non-woven mineral fiber web to an elevated temperature so as to cause said droplets or particles of said heat curable bonding agent to volumetric expand for substantially increasing the bonding agent contact between said mineral fibers of said non-woven fiber web and further so as to cause said heat curable bonding agent to cure for bonding said mineral fibers to one another, thereby forming said mineral fiber web. According to the first aspect of the present invention, a heat ex¬ pandable agent capable of generating a volumetric expansion of the drop¬ lets or particles of the heat curable bonding agent is used for im¬ proving the mechanical properties of the mineral fiber product produced in accordance with the method according to the first aspect of the present invention or alternatively or additionally reducing the amount of heat curable bonding agent of the mineral fiber containing product produced in accordance with the method according to the first aspect of the present invention as compared to the prior art mineral fiber con- taining product of similar or identical mechanical property in terms of mechanical performance, such as modulus of elasticity and strength, and thermal-insulating property. It is to be realized that the heat expandable agent constitutes a component of the heat curable agent such as an amount of typically 0,05% - 1% by weight of the heat curable bonding agent which further constitu¬ tes only a minor percentage of the mineral fiber containing product such as an amount of less than 10%, such as less than 5% of the heat curable bonding agent. According to the prior art, it has been attempted to pro¬ vide composite products containing foamed materials and mineral fibers, vide e.g. DK patent No. 120,579, published European patent application, publiction No. 0058 141, US patent No. 5,123,949 and US patent No. 3,050,427. According to the techniques described in the above US patents and numerous other prior art references, the foamed materials of the prior art are used for providing a composite mineral fiber containing product in which the mineral fibers and the foamed materials of the com¬ posite product provide an integral interlinked and intermeshed struc¬ ture. A totally different usage of the heat expandable agent constitut¬ ing a component of the heat curable bonding agent is accomplished in ac- cordance with the teachings of the present invention as the heat expand¬ able agent according to the teachings of the present invention con¬ stitute only a fraction of the heat curable bonding agent and serve the purpose of causing an expansion of the heat curable bonding agent for increasing the probability that any specific droplet or particle of the heat curable bonding agent is caused to provide a linkage between any two or more adjacent mineral fibers linking the two or more mineral fi¬ bers together after the heat curable bonding agent has been cured and after the heat expandable agent has caused the droplet or particle in question to expand volumetrically. According to the above Danish patent No. 120,579, a composite foamed and mineral fiber product is produced in which product the mineral fibers consitute a filling out of the interspaces between the foamed material. The foamed material is produced by causing a resin to expand by the evaporation of water which resin constitue on the one hand the foamed material and on the other hand the bonding agent linking the mineral fibers together within the foamed structure. The amount of foamed material constitute 5-85% by weight of the total product. In the above published European patent application, a resin- impregnated fiber composite material is described together with a method of producing the material. The material constitute like the above de¬ scribed product known from the above mentioned Danish patent a foamed product including glass or mineral fibers as described. The amount of fibers in the composite material is stated to be 10-150 parts by weight, per 100 parts by weight of the total weight of resin and microspheres, which microspheres are caused, in a low temperature treatment, i.e. a treatment in which the temperature is not raised above 150°C, to expand. The ratio of microspheres to resin is stated to be within the range 15:85 to 30:70. The microspheres are caused to expand and constitute an integral reinforcing structure which is homogeneously distributed in the glass or mineral fibers for producing the integral composite foamed glass or mineral fiber material. According the the presently preferred embodiment of the method ac¬ cording to the present invention, the droplets or particles have dia- meters prior to exposure to the elevated temperature within the range 3- 2,000 /im, such as 10-500 μ , preferably 50-150 μm as it has been rea¬ lized that particles or droplets of diameters smaller than the above range or larger than the above range are likely to provide no linkage between any two or more adjacent mineral fibers or solely provide a large cured or solidified bonding agent sphere which in view of its large diameter preferably should have been substituted by a plurality or smaller diameters droplets or particles providing more linkages between the mineral fibers of the mineral fiber containing product improving the mechanical properties of the mineral fiber containing product. Dependent on the heat curable bonding agent and the heat expandable agent in question and in particular the profile of viscosity and expan¬ sion, respectively, when exposed to heat, the heat expandable agent may be selected so as to provide a volumetric expansion of the heat curable bonding agent within any specific and relevant temperature range within which the heat curable bonding agent is capable of adhering to adjacent mineral fibers and due to capillary action and surface tension proper¬ ties and capable of providing linkage between the mineral fibers. According to the presently preferred embodiment of the method ac¬ cording to the first aspect of the present invention, the heating of the non-woven mineral fiber web comprises a progressive heating of the non- woven mineral fiber web so as to, firstly, cause the heat curable bond¬ ing agent to be less viscous, secondly, cause the heat expandable agent to cause the volumetric expansion of the droplets or particles of the heat curable bonding agent, and, thirdly, cause the heat curable bonding agent to cure. Further preferably, the heat expandable agent generating the volu¬ metric expansion of the droplets or particles of the heat curable bond- ing agent is selected so as to cause the volumetric expansion within a specific relevant temperature range determined by the melting and vis¬ cosity profile of the heat curable bonding agent in question. The heat expandable agent may according to preferred, alternative embodiments ge¬ nerate the volumetric expansion at a temperature of approx. 80-400°C, such as 120-250°C, preferably 150-200°C, and the heat curable bonding agent preferably cures at temperature of approx. 40-40. ---C, preferably 150-200°C. The volumetric expansion of the heat curable bonding agent genera¬ ted by the heat expandable agent may have any physical or chemical origin and thus, according to a first embodiment, the heat expandable agents may be a blowing agent such as an agent liberating a gas, e.g. N 2 , C0 , NH,, or H^O, by exposure to said elevated temperature. Examples of heat expandable agents capable of liberating a gas such as one of the above mentioned gases by exposure to the elevated temperature are azo compounds, carbazides, semi-carbazides, hydrozides or combinations thereof or similar chemical compounds. According to an alternative embo¬ diment, the heat expandable agent is constituted by microspheres each comprising a shell within which a fluid agent is confined. The shell is preferably insoluble by the heat curable bonding agent in order to pre¬ vent that the material of the cell confining the fluid agent is de¬ teriorated by the heat curable bonding agent. The shell may be made of any appropriate material such as thermoplastic material, starch, a poly- eric material, such as PP, PE, PVC, polyacrylamides, acrylonitriles, polybutylenes, a copolymeric material or the like or combinations there¬ of, and said fluid agent being hydrocarbons, such as alcanes, or N 2 , C0 2 , NH, or H 2 0 or the like or combinations thereof. The microspheres should have outer dimensions allowing that the heat curable bonding agent may establish droplets or particles of the above diameter range. Consequently, the microspheres preferably have outer diameters of the order of 1-30 μm, such as 2-10 μm, preferably 2-5 μm. The heat expandable agent constitute as indicated above a con¬ stituent or component of the heat curable bonding agent which further constitutes a minor percentage of the initial mineral fiber containing product. According to a preferred embodiment of the method according to the first aspect of the present invention, the heat expandable agent constitutes approx. 0.02 - 50% by weight of the heat curable bonding agent, such as 0.05 - 5%, preferably 0.05 - 1%. According to a further preferred embodiment of the method according to the first aspect of the present invention, the heat curable bonding agent including the heat expandable agent constitutes less than 5% by weight of the mineral fiber web, such as 1-5%, preferably less than 2%, such as 0,1-2%. The above objects, the above advantages and the above feature to¬ gether with numerous other objects, advantages, and features which will be evident from the below detailed description of preferred embodiments of the invention are in accordance with a second aspect of the present invention obtained by a method of producing a heat curable bonding agent for bonding mineral fibers of a mineral fiber web together, comprising a heat expandable agent capable of generating a volumetric expansion of droplets or particles of said heat curable bonding agent of approx. 2 - 1,000 times, preferably 5 - 500 times, further preferably 10 - 100 times by exposure to an elevated temperature. The heat curable bonding agent according to the second aspect of the present invention is preferably implemented in accordance with the above discussed preferred embodiments of the method according to the first aspect of the present invention. The above objects, the above advantages and the above feature to¬ gether with numerous other objects, advantages, and features which will be evident from the below detailed description of preferred embodiments of the invention are in accordance with a third aspect of the present invention obtained by a method of producing a mineral fiber containing product, containing mineral fibers, said mineral fibers being bonded to¬ gether in an integral structure through a bonding agent initially pre¬ sent in uncured, non-woven mineral fiber webs from which said product is produced as droplets or particles of a heat curable bonding agent and caused to expand through the action of a heat expandable agent capable of generating a volumetric expansion of said droplets or particles of said heat curable bonding agent of approx. 2 - 1,000 times, preferably 5 - 500 times, further preferably 10 - 100 times. The above objects, the above advantages and the above feature to- gether with numerous other objects, advantages, and features which will be evident from the below detailed description of preferred embodiments of the invention are in accordance with a fourth aspect of the present invention obtained by use of a heat expandable agent capable of generat¬ ing a volumetric expansion of droplets or particles of a heat curable bonding agent to be used for bonding mineral fibers of a non-woven mineral fiber web together for causing droplets or particles of said heat expandable bonding agent to volumetric expand approx. 2 - 1,000 times, preferably 5 - 500 times, further preferably 10 - 100 times by exposure to an elevated temperature. The present invention will now be further described with reference to the drawings, in which Fig. 1 is a schematic and perspective view illustrating a first production step of producing a mineral fiber-insulating web from a mine¬ ral fiber forming melt, Fig. 2 is a schematic and perspective view illustrating a second production step of processing the mineral fiber-insulating web produced in the steps shown in Fig. 1, Fig. 3 is a schematic and perspective view illustrating further production steps of curing a mineral fiber-insulating web and of se¬ parating the cured mineral fiber-insulating web into plate segments, Fig. 4 is a diagrammatic view illustrating the viscosity of a heat curable bonding agent in dependency of the temperature of the heat cur- able bonding agent, Fig. 5 is a diagrammatic view illustrating the volumetric expansion of a heat curable bonding agent including a heat expandable agent in de¬ pendency of the temperature of the heat curable bonding agent, Figs. 6a, 6b, 6c and 6d are schematic views illustrating four steps of applying a droplet or a particle of a heat curable bonding agent including a heat expandable agent to a mineral fiber, of volumetrically expanding the droplet or particle through expansion of the heat expand¬ able agent, of contacting the droplet or particle to an adjacent mineral fiber and of curing the heat curable bonding agent so as to bond the mi- neral fibers together, Figs. 7a and 7b are schematic views similar to the views of Figs. 6a and 6b, respectively, illustrating an alternative technique of pro¬ viding volumetric expansion of a droplet or particle of a heat curable bonding agent by means of a sphere including a heat expandable fluid, Fig. 8 is a schematic, sectional and perspective view illustrating a folded mineral fiber-insulating web produced in accordance with the techniques disclosed in DK patent application No. 35/93, Fig. 9 is a schematic and perspective view illustrating a first em¬ bodiment of mineral fiber-insulating plate segment produced in accor- dance with the technique disclosed in DK patent application No. 35/93 and produced from the folded mineral fiber-insulating web shown in Fig. 8, Fig. 10 is a schematic, sectional and perspective view illustrating a folded mineral fiber-insulating web produced in accordance with the techniques disclosed in DK patent applications No. 36/93 or No. 37/93, Fig. 11 is a schematic and perspective view illustrating a second embodiment of a mineral fiber-insulating plate segment produced in ac¬ cordance with the techniques disclosed in DK patent applications No. 36/93 or No. 37/93, Fig. 12 is a schematic and perspective view illustrating a third embodiment of a mineral fiber-insulating plate segment produced in ac¬ cordance with the techniques disclosed in DK patent application No. 36/93 or No. 37/93, Fig. 13 is a schematic, sectional and perspective view of a fourth embodiment of a mineral fiber-insulating plate produced in accordance with the technique disclosed in DK patent application No. 35/93, and Fig. 14 is a schematic, sectional and perspective view of a fifth embodiment of a mineral fiber-insulating plate produced in accordance with the technique disclosed in DK patent application No. 35/93. In Fig. 1, a first step of producing a mineral fiber-insulating web is disclosed. The first step involve the formation of mineral fibers from a mineral fiber forming melt which is produced in a furnace 30 and which is supplied from a spout 32 of the furnace 30 to a total of four rapidly rotating spinning-wheels 34 to which the mineral fiber forming melt is supplied as a mineral fiber forming melt stream 36. As the mine¬ ral fiber forming melt stream 36 is supplied to the spinning-wheels 34 in a radial direction relative thereto, a cooling gas stream is simul- taneously supplied to the rapidly rotating spinning-wheels 34 in the axial direction thereof causing the formation of individual mineral fi¬ bers which are expelled or sprayed from the rapidly rotating spinning- wheels 34 as indicated by the reference numeral 38. By means of two nozzles 35, droplets or particles of a heat curable bonding agent including a heat expandable agent capable of generating a volumetric expansion of the droplets or particles are sprayed onto the mineral fibers 38. The mineral fibers 38 are collected on a continuously operated first conveyer belt 42 forming a primary mineral fiber-insulat¬ ing web 40. The first conveyer belt 42 is, as is evident from Fig. 1, composed of two conveyer belt sections. A first conveyer belt section which is sloping relative to the horizontal direction and relative to a second substantially horizontal conveyer belt section. The first section constitutes a collector section, whereas the second section constitutes a transport section by means of which the primary mineral fiber-insulat- ing web 40 is transferred to a second and a third continuously operated conveyer belt designated the reference numeral 44 and 46, respectively, which are operated in synchronism with the first conveyer belt 42 sand¬ wiching the primary mineral fiber-insulating web 40 between two adjacent surfaces of the second and third conveyer belts 44 and 46, respectively. The second and third conveyer belts 44 and 46, respectively, com¬ municate with a fourth conveyer belt 48 which constitutes a collector conveyer belt on which a secondary mineral fiber-insulating web 50 is collected as the second and third conveyer belts 44 and 46, respective- ly, are swung across the upper surface of the fourth conveyer belt 48 in the transversal direction relative to the fourth conveyer belt 48. The secondary mineral fiber-insulating web 50 is consequently produced by arranging the primary mineral fiber-insulating web 40 in overlapping re- lation generally in the transversal direction of the fourth conveyer belt 48. By producing the secondary mineral fiber-insulating web 50 from the primary mineral fiber-insulating web 40 as disclosed in Fig. 1, a more homogeneous secondary mineral fiber-insulating web 50 is produced as compared to the less homogeneous primary mineral fiber-insulating web 40. It is to be realized that the overall orientation of the mineral fibers of the primary mineral fiber-insulating web 40 is parallel with the longitudinal direction of the web 40 and the direction of transpor- tation of the first conveyer belt 42. Contrary to the primary mineral fiber-insulating web 40 the overall orientation of the mineral fibers of the secondary mineral fiber-insulating web 50 is substantially perpendi¬ cular and transversal relative to the longitudinal direction of the se¬ condary mineral fiber-insulating web 50 and the direction of transporta- tion of the fourth conveyer belt 48. In Fig. 2, a station 60 is shown for processing the secondary mi¬ neral fiber insulating web 50 or alternatively the primary mineral fiber-insulating web 40 provided the transport section comprising the conveyer belts 44 and 46 are omitted such as for compacting and homoge- nizing the mineral fiber-insulating web being the primary or secondary mineral fiber-insulating web input to the station 60. The station 60 may be implemented in accordance with the teachings described in DK patent application No. 35/93, No. 36/93 or No. 37/93. The station 60 comprises two sections 62 and 64 which are arranged at opposite sides of the mine- ral fiber-insulating web input to the station 60 and serve the purpose of processing the input mineral fiber-insulating web for producing an output mineral fiber-insulating web, which output mineral fiber-insulat¬ ing web is more compact and more homogeneous as compared to the mineral fiber-insulating web input to the station 60. The output mineral fiber- insulation web produced in the station 60 may further as shown in Fig. 2 be composed of a low compactness body or center core 54 and a compacted top layer 56. In Fig. 3, the mineral fiber-insul ating web assembly produced as discussed above with reference to Fig. 2 and including the low compact¬ ness body or center core 54 and the compacted surface layer 56 is moved through a curing station 70 constituting a curing oven or curing furnace comprising oppositely arranged curing oven sections 72 and 74, which ge- nerate heat for heating the mineral fiber-insulating web assembly to an elevated temperature so as to cause the heat expandable agent of the heat curable bonding agent to generate a volumetric expansion of the droplets or particles of the heat curable bonding agent as will be de¬ scribed in greater details below, and so as to cause the heat-curable bonding agent of the mineral fiber-insulating web assembly to cure and cause the mineral fibers of the central core or the body of the assembly and the f ibers of the compacted surface layer to be bonded together so as to form an integral bonded mineral fiber-insulating web which is cut into plate-like segments by means of a knife 76. In Fig. 3, a single plate-like segment 10 is shown comprising a central core 12 and a top layer 14. The top layer 14 is made from the compacted surface layer 56, whereas the core 12 is made from the low compactness body or central core 54 of the corrugated and longitudinally folded mineral fiber- insulating web shown in Fig. 2. Figs. 4 and 5 are diagrammatic views illustrating the dependency of the viscosity of the heat curable bonding agent used in the first step of producing a mineral fiber-insulating web shown in Fig. 1 and the vo¬ lumetric expansion of the heat curable bonding agent through the action of a heat expandable agent included in the heat curable bonding agent, respectively, in dependency of the temperature of the heat curable bond¬ ing agent. Along the abcissa axes, the temperature is indicated in C°, along the ordinate axis of the diagramme of Fig. 4, the viscosity of the heat curable bonding agent is indicated in logarithmic scale, and along the ordinate axis of the diagramme of Fig. 5, the volume of the heat curable bonding agent is indicated in linear scale. In Fig. 4, a curve A illustrates the profile of viscosity change of the heat curable bonding agent as the heat curable bonding agent is heated from a low temperature to a high temperature. In Fig. 5, a curve B illustrates the volumetric expansion of the heat curable bonding agent as the heat curable bonding agent is heated from the low temperature to the elevated temperature. In Figs. 4 and 5, four temperatures T,, T 2 , T, and T. are indicated. The temperature T, is a temperature of approx. 70-80°C at which the viscosity of the heat cur- able bonding agent decreases, until a minimum viscosity area correspond¬ ing to the temperature interval T 2 -T 3 of approx. 90-120°C, within which interval any water present within the heat curable bonding agent evaporates. Within the interval T--T. the heat expandable agent of the heat curable bonding agent causes a volumetric expansion of the heat curable bonding agent. An elevated temperature T. corresponding to a temperature of approx. 170-200°C corresponds to the temperature at which the maximum volumetric expansion of the heat curable bonding agent has been produced and at which the viscosity of the heat curable bonding agent has also increased during the process of curing the heat curable bonding agent. Beyond the temperature T,, the volumetric expansion cap¬ ability of the heat expandable agent of the heat curable bonding agent may have decreased as the bonding may have solidified or as the heat ex¬ pandable agent may have evaporated or deteriorated, as will be described below with reference to Figs. 6 and 7. In Fig. 6a, two mineral fibers 20 and 22 are shown which mineral fibers are produced at the first step of producing a mineral fiber- insulating web described above with reference to Fig. 1. In Fig. 6a, a particle or droplet 24 of a heat curable bonding agent including a heat expandable agent such as a blowing agent is also shown which droplet or particle is applied to the mineral fiber 22 in a position in which the droplet or particle 24 provides no adhesion between the mineral fiber 22 and the mineral fiber 20 as the droplet or particle 24 provides no con¬ tact with the mineral fiber 22. As the mineral fiber-insulating web containing the mineral fiber 20 and 22 is introduced into the curing station described above with refe¬ rence to Fig. 3, the heat curable bonding agent is exposed to a tempera¬ ture profile such as the temperature profile described above with re¬ ference to Fig. 4 and also exposed to volumetric expansion caused by the heat expandable agent of the heat curable agent. As the heat curable agent expands as shown i Fig. 6b, the droplet or particle shown in Fig. 4 is expanded into a somewhat enlarged droplet or particle 25 shown in Fig. 6b which establishes contact with the mineral fiber 20 as indicated by the reference numeral 26 still maintaining the contact with the mine- ral fiber 22 as indicated by the reference numeral 27. As the heat curable bonding agent including the heat expandable agent is exposed to a further temperature increase, the droplet or par¬ ticle 25 shown in Fig. 6b is caused to further expand and due to the viscosity of the heat curable bonding agent and further capillary action and surface tension of the expanded droplet or particle caused to pro¬ vide an enlarged contact area between the mineral fibers 20 and 22 as indicated by the reference numeral 28 shown in Fig. 6b. As the mineral fibers 20 and 22 and the heat curable bonding agent is further exposed to heat, the heat curable bonding agent cures and provides a cured or solidified linkage between the mineral fibers 20 and 22 as indicated by the reference numeral 29 shown in Fig. 6d. The volumetric expansion of the heat curable bonding agent droplets or particles may alternatively be provided through microspheres includ¬ ing a heat expandable fluid or gas which microspheres are suspended within the heat curable bonding agent. In Fig. 7a, the droplet or particle 24 is shown including a micro¬ sphere 23 including a heat expandable fluid such as water or a gaseous hydrocarbon composition. As the droplet or particle 24 shown in Fig. 7a is exposed to heat, the microsphere 23 expands through the action of the heat expandable fluid contained within the microsphere 23 providing a radically enlarged microsphere 23' contained within the droplet or par¬ ticle 25' corresponding to the droplet or particle 25 described above with reference to Fig. 6b. As the microsphere 23' is further heated, the microsphere may burst causing a further enlargement of the heat curable bonding agent contact between the mineral fibers 20 and 22 as shown in Fig. 6c. Below alternative embodiments of mine*-" 1 fiber-insulating webs and plate segments are to be described, in whic. embodiments the technique of volumetric expanding the heat curable bonding agent by means of a heat expandable agent during the process of curing the heat curable bonding agent or prior to the process of curing the heat curable bonding agent is implemented. In Fig. 8, a vertical sectional view of a corrugated and trans- versally folded mineral fiber-insulated web 10' produced in accordance with the teachings of DK patent application No. 35/93 is shown. The cor¬ rugated and transversally folded mineral fiber-insulating web 10' com¬ prises a central core or body 18' and two oppositely arranged surface layers 14' and 16', which surface layers 14' and 16' are separated from the central core or body 18' of the corrugated and transversally folded mineral fiber-insulating web 10' along imaginary lines of separation, shown in dotted line. The surface layers 14' and 16' of the corrugated and transversally folded mineral fiber-insulating web 10' are composed of segments of the folded mineral fiber-insulating web which segments contain mineral fibers which are orientated substantially longitudinally relative to the longitudinal direction of the corrugated and trans- versally folded mineral fiber-insulating web 10'. The central core or body 18' of the corrugated and transversally folded mineral fiber-insulating web 10' is composed of segments of the folded mineral fiber-insulating web 10' which segments are folded per¬ pendicular to the segments of the surface layers 14' and 16' of the mi- neral fiber-insulating web 10'. The fibers of the central core of body 18' of the corrugated and transversally folded mineral fiber-insulating web 10' are orientated substantially perpendicular to the longitudinal direction as well as the transversal direction of the corrugated and longitudinally folded mineral fiber-insulating web 10'. In Fig. 9, a fragmentary and perspective view of a first embodiment of a plate segment 10" is shown. The plate segment 10" is produced in accordance with the teachings of DK patent application No. 35/93 from the corrugated and transversally folded mineral fiber-insulating web 10' also shown in Fig. 8 and comprises a central core 18" and a top layer 14". In Fig. 10, a vertical sectional view of a corrugated and longitu¬ dinally folded mineral fiber-insulated web 10'" is shown. The corruga¬ ted and longitudinally folded mineral fiber-insulating web 10'" is pro¬ duced in accordance with the teachings of DK patent applications No. 36/93 or No. 37/93 and comprises a central core or body 18'" and two oppositely arranged surface layers 14'" and 16'", which surface layers 14'" and 16"' are separated from the central core or body 18'" of the corrugated and longitudinally folded mineral fiber-insulating web 10'" along imaginary lines of separation shown in dotted line in Fig. 14. The surface layers 14'" and 16'" of the corrugated and longitudinally folded mineral fiber-insulating web 10'" are composed of segments of the folded mineral fiber-insulating web which segments contain mineral fibers which are orientated substantially transversally relative to the longitudinal direction of the corrugated and longitudinally folded mine- ral fiber-insul ating web 10' " . The central core or body 18'" of the corrugated and longitudinally folded mineral fiber-insulating web 10'" is composed of segments of the folded mineral fiber-insulating web 10"' which segments are folded per- pendicular to the segments of the surface layers 14'" and 16'" of the mineral fiber-insulating web 10'". The fibers of the central core of body 18'" of the corrugated and longitudinally folded mineral fiber- insulating web 10'" are orientated substantially perpendicular to the longitudinal direction as well as the transversal direction of the cor¬ rugated and longitudinally folded mineral fiber-insulating web 10'". In Fig. 11, a fragmentary and perspective view of a second embodi¬ ment of a plate segment according to the present invention and produced in accordance with the teachings of DK patent application No. 36/93 and 37/93 is shown, designated the reference numeral 10"" in its entirety. The plate segment 10"" comprises a central core 18"" and a top layer 14"" and further a bottom layer 16"" made from the surface layers 14'" and 16'", respectively, of the mineral fiber-insulating web 10'" shown in Fig. 10. In Fig. 12, a fragmentary and perspective view of a third embodi¬ ment of a plate segment of a mineral fiber-insulating web according to the present invention is shown, designated the reference numeral 10 in its entirety. Like the plate segment 10"", described above with refe- w rence to Fig. 11, the plate segment 10 comprises the central core 18"", the top layer 14"" and the bottom layer 16"". Moreover, a top surface covering 19 is provided. The top surface covering 19 may constitute a web of a plastics material, a woven or non-woven plastic foil, or alternatively a covering made from a non-plastics material, such as a paper material serving design and architectural purposes exclusively. The top surface layer 19 may alternatively be applied to the mineral fiber-insulating web after the expansion of the heat curable bonding agent generated by the heat expandable agent and the curing of the heat-curing, bonding agent, i.e. after the exposure to heat genera¬ ted by the oven sections 72 and 74 shown in Fig. 3. In Fig. 13, a fragmentary and perspective view of a fourth embodi- VI ment of a mineral fiber-insulating plate assembly 10 is shown. The mineral fiber-insulating plate assembly 10 comprises a central VI core or body 18 produced from a folded mineral fiber-insulating web as disclosed in DK patent application No. 35/93 and a compacted surface layer 14 VI In Fig. 14, a fragmentary and perspective view of a fifth embodi VII ment of a mineral fiber-insulation plate assembly 10 is shown. Liki the fourth embodiment described above with reference to Fig. 13, the fifth embodiment comprises the central core 18 and the top layer 14 Moreover, a top surface covering 19 is provided. EXAMPLE Mineral fibers of an average diameter of 5 μm were coated with droplets of an average diameter of 50-150 μm of a heat curable bonding agent constituted by an aqueous solution of resin constituting 2% by weight of the finished product. The droplets contained spheres of acry- lonitrilvinylidenchloride of an amount of approx. 0.5% by weigth of the heat curable bonding agent. The mineral fibers and the heat curable bon¬ ding agent including the heat expandable agent were heated in a curing oven prodiving a heating profile substantially as described above with reference to Figs. 4 and 5. A mineral fiber containing product of a den- 3 sity of 35 kg/m was produced. The characteristics as to mechanical per¬ formance and the thermal insulating property of this product were identical to those of a conventional mineral fiber containing product of identical density, however, including a much larger amount of cured bonding agent.

Claims: CLAIMS : 1. A method of producing a mineral fiber web, comprising: producing a non-woven mineral fiber web including mineral fibers and droplets or particles of a heat curable bonding agent including a heat expandable agent capable of generating a volumetric expansion of said droplets or particles of approx. 2 - 1,000 times, preferably 5 - 500 times, further preferably 10 - 100 times, by exposure to an elevated temperature, and heating said non-woven mineral fiber web to an elevated temperature so as to cause said droplets or particles of said heat curable bonding agent to volumetric expand for substantially increasing the bonding agent contact between said mineral fibers of said non-woven fiber web and further so as to cause said heat curable bonding agent to cure for bonding said mineral fibers to one another, thereby forming said mineral fiber web. 2. The method according to Claim 1, said droplets or particles having diameters prior to exposure to said elevated temperature within the range 3 - 2,000 μm, such as 10 - 500 μm, preferably 50 - 150 μm. 3. The method according to any of the Claims 1-2, said heating of said non-woven mineral fiber web comprising a progressive heating of said non-woven mineral fiber web so as to, firstly, cause said heat cur¬ able bonding agent to be less viscous, secondly, cause said heat ex¬ pandable agent to cause said volumetric expansion of said droplets or particles of said heat curable bonding agent, and, thirdly, cause said heat curable bonding agent to cure. 4. The method according to any of the Claims 1-3, said heat expan¬ dable agent generating said volumetric expansion of said droplets or particles at a temperature of approx. 80-400°C, such as 120-250°C, pre- ferably 150-200°C, and said heat curable bonding agent curing at a tem¬ perature of approx. 40-400°C, preferably 150-200°C. 5. The method according to any of the Claims 1-4, said heat expan¬ dable agent being a blowing agent such as an agent liberating a gas, e.g. N 2 , C0 2 , NH 3 , or H 2 0, by exposure to said elevated temperature. 6. The method according to Claim 5, said heat expandable agent be¬ ing azo compounds, carbazides, semicarbazides, hydrazides or the like or combinations thereof. 7. The method according to any of the Claims 1-4, said heat expan- dable agent being constituted by microspheres each comprising a shell within which a fluid agent is confined. 8. The method according to Claim 7, said shell being insoluble by said heat curable bonding agent. 9. The method according to any of the Claims 7 or 8, said shell be¬ ing made of a thermoplastic material, starch, a polymeric material, such as PP, PE, PVC, polyacrylamides, acrylonitriles, polybutylenes, a co- polymeric material or the like or combinations thereof, and said fluid agent being hydrocarbons, such as alcanes, or N 2 , C0 2 , NH, or H 2 0 or the like or combinations thereof. 10. The method according to any of the Claims 7-9, said micro¬ spheres having outer diameters of the order of 1-30 μm, such as 2-10 μm, preferably 2-5 μm. 11. The method according to any of the Claims 1-10, said heat ex- pandable agent constituting approx. 0.02-50 % by weight of said heat curable bonding agent, such as 0.05-5%, preferably 0.05-1%. 12. The method according to any of the Claims 1-11, said heat cur¬ able bonding agent including said heat expandable agent constituting less than 5% by weight of said mineral fiber web, such as 1-5%, prefer- ably less than 2%, such as 0,1-2%. 13. A heat curable bonding agent for bonding mineral fibers of a mineral fiber web together comprising a heat expandable agent capable of generating a volumetric expansion of droplets or particles of said heat curable bonding agent of approx. 2 - 1,000 times, preferably 5 - 500 times, further preferably 10 - 100 times by exposure to an elevated tem¬ perature. 14. The heat curable bonding agent according to Claim 13, said heat expandable bonding agent being a blowing agent such as an agent liberat¬ ing a gas, e.g. N 2 , C0 2 , NH- or H 2 0, by exposure to said elevated tempe- rature. 15. The heat curable bonding agent according to Claim 14, said heat expandable agent being azo compounds, carbazides, semicarbazides, hydra- zides or the like or combinations thereof. 16. The heat curable bonding agent according to any of the Claims 13-15, said heat expandable agent being constituted by microspheres each comprising a shell within which a fluid agent is confined. 17. The heat curable bonding agent according to Claim 16, said shell being insoluble by said heat curable bonding agent. 18. The heat curable bonding agent according to any of the Claims 16 or 17, said shell being made of a thermoplastic material, starch, a polymeric material such as PP, PE, PVC, polyacrylamides, acrylonitriles, polybutylenes, a copolymeric material or the like or combinations there- of, and said fluid agent being hydrocarbons, such as alcanes, or N 2 , C0 2 , NH 3 or H 2 0 or the like or combinations thereof. 19. A mineral fiber containing product containing mineral fibers, said mineral fibers being bonded together in an integral structure through a bonding agent initially present in uncured, non-woven mineral fiber webs from which said product is produced as droplets or particles of a heat curable bonding agent and caused to expand through the action of a heat expandable agent capable of generating a volumetric expansion of said droplets or particles of said heat curable bonding agent of ap¬ prox. 2 - 1,000 times, preferably 5 - 500 times, further preferably 10 - 100 times. 20. Use of a heat expandable agent capable of generating a volu¬ metric expansion of droplets or particles of a heat curable bonding agent to be used for bonding mineral fibers of a non-woven mineral fiber web together for causing droplets or particles of said heat expandable bonding agent to volumetric expand approx. 2 - 1,000 times, preferably 5 - 500 times, further preferably 10 - 100 times by exposure to an eleva¬ ted temperature.

Inventors: CLAUSEN ANDERS ULF, CLAUSEN, ANDERS, ULF
Applicants: CLAUSEN ANDERS ULF, ROCKWOOL INT, CLAUSEN, ANDERS, ULF, ROCKWOOL INTERNATIONAL A/S
Application year: 1994
Main classification: C03C25
IPC codes: C03C25, C08J9